MECHATRONICS CORRECT EXAMS SCRIPT
QUESTIONS AND ANSWERS SURE A+
✔✔Logic Gates - ✔✔-AND Gate: output is 1 only if all inputs are 1
-OR Gate: Output is 1 if at least one input is 1
- NOT Gate: It has only one input and flips it (1 becomes 0)
- XOR Gate: Output 1 only if inputs are different
- NAND/NOR: inverted versions of AND and OR
✔✔Op-Amp - ✔✔-Can be used as a voltage amplifier
-An op amps inputs draw essentially no current. In other words, op amps have a very
large input impedance, so their inputs work off of voltage levels alone
- When an op amp is wired with negative feedback (output is connected back to its
inverting input), op amp will automatically output whatever it needs to (in terms of
voltage and current i.e., power) in order to balance the voltage at its inverting input to
match whatever voltage that it sees at its non-inverting input
- Most basic function is to act as a comparator. If non-inverting input has a larger
voltage than its inverting ijnput, the op-amp will output its positive supply voltage. Does
the opposite if vice versa.
- Comparator is the first circuit, voltage follower is the second, voltage amplifier is the
third
- Voltage amplifier: adds negative feedback to allow the gain of an op amp to be limited
and controlled (its not when used solely as a comparator). Connect output directly back
to inverting input.
- Voltage Amplifier: Place a voltage divider after output that divides output to some
lower voltage before feeding it back to the inverting input
Gain = Vout/Vin
✔✔Open-Loop vs Closed-Loop Control - ✔✔-Open loop systems perform actions based
on a preset instruction without checking results. Input --> controller --> actuator -->
output. Essentially a blind system
- Closed loop systems measures the output and compares to a desired goal. Self
adjusts based on error. Set point (goal) --> controller --> actuator --> output -->
sensor/feedback --> back to setpoint (completes a closed loop)
, ✔✔Servo Systems - ✔✔-Remote control servos are closed loop systems that use a
potentiometer wired as a voltage divider to communicate it's actual position as an
analog voltage to compare to the setpoint (desired position in this case). Acts as an
absolute encoder
- Servo systems just imply that a system is closed-loop. RC servos are actually
controlled in an open-loop way since the microcontroller that is sending control signals
to it never receives any feedback that the RC servomotor is actually obeying its
commands (this is why stall is such a big deal).
✔✔DC Brush Motors - ✔✔- Direct current brush motors which are the most common
type of actuator found in mechatronic systems and are controlled via pulse width
modulation and H-bridge circuits
-Speed is contolled by voltage (PWM typically)
-Direction is controlled by polarity (controlled by the H-Bridge. See which of the four
switches are on or off
-Open-loop system until you attach an encoder to monitor position
✔✔DC Brushless Motors - ✔✔-Motor that combines the durability of stepper motors and
the smooth continuous rotation characteristics of DC brush motors
- The mechanical commutator is replaced with transistors and computer control. DC
brushless motors also typically have magnets on the rotor with the electromagnetic coils
attached to the surrounding stator.
✔✔AC Induction Motors - ✔✔- Motor where the rotor is powered by electromagnetic
induction rather than physical brushes or permanent magnets
- AC power in the stator creates a rotating magnetic field that the rotor "chases"
- To change the motors speed, use a variable frequency drive. This takes power and
changes its frequency
✔✔Servo Motors - ✔✔- Servo motor is just any motor that is paired with a sensor for
closed-loop position or velocity feedback
-RC servo motors are an example of this. They typically use a small DC motor, a
gearbox, and a control circuit and put it into a single housing. Feedback comes from a
simple potentiometer connected to the output shaft to tell the internal circuit where the
arm is. Can only rotate between 0 and 180 degrees because the potentiometer
✔✔Stepper Motors - ✔✔- Controlled typically in an open-loop fashion. The rotor is made
up of an array of permanent magnets and the stator surrounding the rotor contains
electromagnetic coil windings separated into phases. The phases are switched on and
off in a specific sequence in order to rotate. Move in discrete steps, like ours which
moves in 1.8 degree increments.
- Can rotate to 360 degrees and beyond
- Unipolar: Current only flows in one direction through each coil. Are wired in parallel
and operate well at high speeds.
QUESTIONS AND ANSWERS SURE A+
✔✔Logic Gates - ✔✔-AND Gate: output is 1 only if all inputs are 1
-OR Gate: Output is 1 if at least one input is 1
- NOT Gate: It has only one input and flips it (1 becomes 0)
- XOR Gate: Output 1 only if inputs are different
- NAND/NOR: inverted versions of AND and OR
✔✔Op-Amp - ✔✔-Can be used as a voltage amplifier
-An op amps inputs draw essentially no current. In other words, op amps have a very
large input impedance, so their inputs work off of voltage levels alone
- When an op amp is wired with negative feedback (output is connected back to its
inverting input), op amp will automatically output whatever it needs to (in terms of
voltage and current i.e., power) in order to balance the voltage at its inverting input to
match whatever voltage that it sees at its non-inverting input
- Most basic function is to act as a comparator. If non-inverting input has a larger
voltage than its inverting ijnput, the op-amp will output its positive supply voltage. Does
the opposite if vice versa.
- Comparator is the first circuit, voltage follower is the second, voltage amplifier is the
third
- Voltage amplifier: adds negative feedback to allow the gain of an op amp to be limited
and controlled (its not when used solely as a comparator). Connect output directly back
to inverting input.
- Voltage Amplifier: Place a voltage divider after output that divides output to some
lower voltage before feeding it back to the inverting input
Gain = Vout/Vin
✔✔Open-Loop vs Closed-Loop Control - ✔✔-Open loop systems perform actions based
on a preset instruction without checking results. Input --> controller --> actuator -->
output. Essentially a blind system
- Closed loop systems measures the output and compares to a desired goal. Self
adjusts based on error. Set point (goal) --> controller --> actuator --> output -->
sensor/feedback --> back to setpoint (completes a closed loop)
, ✔✔Servo Systems - ✔✔-Remote control servos are closed loop systems that use a
potentiometer wired as a voltage divider to communicate it's actual position as an
analog voltage to compare to the setpoint (desired position in this case). Acts as an
absolute encoder
- Servo systems just imply that a system is closed-loop. RC servos are actually
controlled in an open-loop way since the microcontroller that is sending control signals
to it never receives any feedback that the RC servomotor is actually obeying its
commands (this is why stall is such a big deal).
✔✔DC Brush Motors - ✔✔- Direct current brush motors which are the most common
type of actuator found in mechatronic systems and are controlled via pulse width
modulation and H-bridge circuits
-Speed is contolled by voltage (PWM typically)
-Direction is controlled by polarity (controlled by the H-Bridge. See which of the four
switches are on or off
-Open-loop system until you attach an encoder to monitor position
✔✔DC Brushless Motors - ✔✔-Motor that combines the durability of stepper motors and
the smooth continuous rotation characteristics of DC brush motors
- The mechanical commutator is replaced with transistors and computer control. DC
brushless motors also typically have magnets on the rotor with the electromagnetic coils
attached to the surrounding stator.
✔✔AC Induction Motors - ✔✔- Motor where the rotor is powered by electromagnetic
induction rather than physical brushes or permanent magnets
- AC power in the stator creates a rotating magnetic field that the rotor "chases"
- To change the motors speed, use a variable frequency drive. This takes power and
changes its frequency
✔✔Servo Motors - ✔✔- Servo motor is just any motor that is paired with a sensor for
closed-loop position or velocity feedback
-RC servo motors are an example of this. They typically use a small DC motor, a
gearbox, and a control circuit and put it into a single housing. Feedback comes from a
simple potentiometer connected to the output shaft to tell the internal circuit where the
arm is. Can only rotate between 0 and 180 degrees because the potentiometer
✔✔Stepper Motors - ✔✔- Controlled typically in an open-loop fashion. The rotor is made
up of an array of permanent magnets and the stator surrounding the rotor contains
electromagnetic coil windings separated into phases. The phases are switched on and
off in a specific sequence in order to rotate. Move in discrete steps, like ours which
moves in 1.8 degree increments.
- Can rotate to 360 degrees and beyond
- Unipolar: Current only flows in one direction through each coil. Are wired in parallel
and operate well at high speeds.
